I don't know, and I don't really care. But I smell a race condition here. Are you using proper file locking to prevent two nearly parallel processes from overwriting the single storage file with out-of-date data?

File locking is highly OS dependant. There are several ways to lock a file, and most times, only one of them really protects you from race conditions. And it even gets worse when network drives are added. For that reason, and because I most times already have and use a database, I prefer using a relational database for storing sessions. It doesn't really matter which one, all of the big players (PostgreSQL, Oracle, MySQL, MS SQL Server) have working locking mechanisms, so I don't have to care about file locking. SQLite should also work, at least on a local file system on Unix derivates. I'm not sure about SQLite's file locking on Windows and on network drives, there may be problems.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

I'm likely to go with a MySQL solution. Things like race conditions can cause unexpected behaviour and so difficult to troubleshoot. Furthermore, I have only used Storable briefly as an exploration, so don't know much about it and might be problematic to troubleshoot if things go wrong.